Core samples of a submerged bottom can be obtained by dropping a cable-suspended core barrel from a floating vessel through the water so that the open lower end of the barrel penetrates the bottom and thereby cuts a sample which is retained in the barrel. The barrel is raised to above the surface of the water and the core sample is removed for analysis. Typically the barrel is fitted with an internal light-weight core tube which receives the sample during penetration of the bottom, and the tube and sample are removed together from the barrel. An empty tube is inserted in the barrel before the next sample-taking operation.
The core barrel assembly, being cable-suspended at its upper end, must be prevented from swinging as a result of wave action on the floating vessel. It is known to support a rigid guide tube from or on the vessel for telescopically receiving the core barrel when the latter is in a raised position and for guiding the assembly at the beginning of its free fall toward the submerged bottom.
So far as the applicant is aware prior core sampling systems have required that the vessel not be underway during the taking of a sample, due to the construction and/or location of the guide structure for the core barrel assembly. That is, the vessel needed to be stationary, in the sense of not being propelled through the water, during dropping and raising of the core barrel assembly in order to avoid entangling the cable in the screw and/or to avoid unduly high stresses in the guide structure.